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Soil Moisture Measurement

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Thanks to our electronic weather stations we can measure soil moisture continuously in site. With this we can see how the plant takes out the water and when it needs irrigation. For iMETOS we can offer sensors following the two major principles: 

  • The tensiometric principlee measuring soil water suction
  • The volumetric principle measuring soil water content in volume parts.

All soil water fixed in small pores and capillaries is hold force of gravity. The holding force is a function of the pore size and the surface tension of the water. The water suction can be measured by devises like tensiometers or gypsum blocks (watermark sensors). If the water contend of a soil is over field capacitance a portion of the water is inside of big pores and this water is moved by gravity. Water suction measuring devices can not be used to measure in this area. In an ideal soil all pores and capillaries can to be assumed to be connected. With this the whole soil will show the same water suction if we can wait long enough. In reality we will find some horizontal and vertical distribution of soil water suction too do to the fact that rain or irrigation is reaching the top soil layer first and plant roots are extracting water in restricted areas of the soil.

The volumetric water contend of the soil is containing all water independent if it is filling big pores and it is moving trough the soil by gravity or if it is fixed inside the soil minerals. Therefore the data about volumetric soil water contend can tell us nothing about the plant availability of the water. To learn about the water needs of an specific crop on a specific site we will have to apply some external data or we will have to analyse longer time series of data.

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Created by system. Last Modification: Monday 21 of May, 2012 14:04:34 GMT by Lena.